The present invention relates to a stair-climbing wheelchair carrier designed to transport a wheelchair up and down stairs.
Japanese Patent No. 2551862 shows a typical stair-climbing wheelchair carrier. This prior art example is first described with reference to FIG. 1A and FIG. 1B, which illustrate the wheelchair carrier moving on a level ground and on stairs, respectively. The wheelchair carrier 1 is generally made up of a wheelchair carrying platform 2 and a crawler drive unit 3. The wheelchair carrying platform 2 is pivoted by a shaft 4 at one end (rear side of the wheelchair K carried thereon) to the crawler drive unit 3. An extension/retraction cylinder 5 is pivoted at one end to the wheelchair carrying platform 2 and at the other end to the crawler drive unit 3, so that the wheelchair carrying platform 2 can be inclined relative to the crawler drive unit 3 by extension and retraction of the cylinder 5.
The wheelchair carrying platform 2 includes a frame 20 that forms a left and right wheelchair carrying floor 21 and a bridge accommodating space 22 therebelow. One end of the above-mentioned cylinder 5 is pivoted to this frame 20. To the frame 20 are attached wheels, for example, one front wheel 23A and two rear wheels 23B. When the cylinder 5 is completely retracted, these wheels make contact with the ground as shown in FIG. 1A, making a space under the crawler drive unit 3, so that the wheelchair carrier 1 can run with the wheels 23A and 23B on a level ground.
A retaining handle 24 stands generally at right angles to the frame 20 near one end of the wheelchair carrying platform 2 (rear side of the wheelchair K carried thereon). At the top of this retaining handle 24 are provided a grip 24A and an operation unit 25. An operator of the stair-climbing wheelchair carrier 1 controls the extension and retraction of the cylinder 5 and the drive of the crawler drive unit 3 through the operation unit 25 while holding the grip 24A. To the retaining handle 24 is attached a safety belt 26 with a buckle 26A, which is worn around the wheelchair user K1 so as to retain the wheelchair K to the retaining handle 24.
The crawler drive unit 3 has a pair of track frames 30 on the left and right which are bent upwards at one end so that they look like a sledge from a side view. The other ends of the left and right track frames 30 are coupled together by a reduction gear case (not shown) in which a drive motor 31 and a reduction gear (not shown) are integrated. These track frames 30 coupled together form the main body of a frame structure, on one end of which a battery 32 that supplies power to the drive motor 31 is mounted.
Drive wheels 34 are attached to drive shafts 33 or output shafts of the reduction gear on the left and right. Crawler belts 36 are trained around the drive wheels 34 and idle wheels 35 attached at the left and right sledge-shaped ends of the track frames 30. The crawler belts 36 move along a ground guide 30A of the track frames 30 and an inclined guide 30B in the sledge-shaped part on the lower side of the crawler drive unit 3, and are pressed down by press rollers 37 pivoted by the shaft 4 on the upper side, so that they make contact with corners of two or more stairs S when moving up and down as shown in FIG. 1B.
To use this conventional stair-climbing wheelchair carrier 1, a bridge (not shown) is drawn out from the bridge accommodating space 22 on a level ground so that the wheelchair K rides onto the bridge and rests on the floors 21 as shown in FIG. 1A. After the safety belt 26 is worn around the wheelchair user K1 and fastened with the buckle 26A, the cylinder 5 is controlled through the operation unit 25 to extend, so that the wheelchair carrying platform 2 is tilted backward relative to the crawler drive unit 3.
When going up stairs, the drive motor 31 is driven through control from the operation unit 25 to cause the sledge-shaped inclined part of the crawler belts 36 of the crawler drive unit 3 to make contact with a first stair of the staircase so that the crawler drive unit 3 rides on the stair and goes up the stairway as shown in FIG. 1B. When going down stairs, the crawler belts 36 are brought into contact with the first stair on the opposite side from the sledge-shaped end of the crawler drive unit 3, and the wheelchair carrier travels down as shown in FIG. 1B.
With this conventional stair-climbing wheelchair carrier, the inclination angle of the wheelchair carrying platform 2 relative to the crawler drive unit 3 when traveling up and down the stairs S as shown in FIG. 1B is set such that the wheelchair K carried on the floors 21 is slightly tilted backward from the vertical. That is, when the maximum inclination angle of stairs that the stair-climbing wheelchair carrier 1 is designed to accommodate is 35°, the wheelchair carrying platform 2 can be inclined up to 40° relative to the crawler drive unit 3. The floors 21 are tilted backward from the horizontal at about 5° when moving up and down the stairs so as to give the wheelchair user K1 the feeling of safety.
However, because of such platform inclination angle setting (e.g. 40° if the stair angle is 35°), the wheelchair carrying platform 2 is largely tilted backward on a level ground or a landing between stairs before or after ascending or descending the stairs. Therefore, the wheelchair user K1 carried on the floors 21 may feel uncomfortable because the wheelchair carrying platform 2 is so tilted backward that the user almost faces the ceiling.
Moreover, when the wheelchair carrying platform 2 is largely inclined backward relative to the generally horizontal crawler drive unit 3, the retaining handle 24 of the wheelchair carrying platform 2 is also inclined backward, requiring a large space at the back. The wheelchair carrier therefore may be unusable in a confined area such as a landing or the like because of lack of operation space.